100408 no.04-hydrothermal synthesis of nanomaterials-guo(1)

8/2/2019 100408 No.04-Hydrothermal Synthesis of Nanomaterials-GUO(1)

1/22

Hydrothermal /Hydrothermal / SolvothermalSolvothermal

Synthesis ofSynthesis of NanomaterialsNanomaterials

YuYu--GuoGuo GuoGuo

2010.4.82010.4.8


2/22

Hydrothermal /Hydrothermal /SolvothermalSolvothermal Synthesis ofSynthesis of

NanomaterialsNanomaterials

ContentContent

What is hydrothermal /What is hydrothermal /solvothermalsolvothermal synthesis?synthesis?

What is the main characteristics ofWhat is the main characteristics of

hydrothermal /hydrothermal /solvothermalsolvothermal synthesis?synthesis? Examples of synthesis ofExamples of synthesis ofnanomaterialsnanomaterials viavia

hydrothermal /hydrothermal /solvothermalsolvothermal methodmethod


3/22

Introduction to hydrothermalIntroduction to hydrothermal

techniquestechniques

The hydrothermal technique has been most popular,

garnering interest from scientists and technologists ofdifferent disciplines, particularly in the last fifteen

years. The term hydrothermal is purely of geological

origin. It was first used by the British Geologist, SirRoderick Murchison (17921871), to describe the

action of water at elevated temperature and pressure

in bringing about changes in the earths crust leadingto the formation of various rocks and minerals.


4/22

Introduction to hydrothermalIntroduction to hydrothermal

techniquestechniquesThe hydrothermal synthesis has been successful for

the preparation of important solids such asmicroporous crystals, superionic conductors,

chemical sensing oxides, electronically conducting

solids, complex oxide ceramics and fluorides,magnetic materials, and luminescence phosphors. It

is also a route to unique condensed materials

including nanometer particles, gels, thin films,distinguished helical and chiral structures, and

particularly-stacking-sequence materials.


5/22

What is hydrothermal /What is hydrothermal /solvothermalsolvothermal

synthesis?synthesis?

Hydrothermal synthesis refers to the synthesis by chemical

reactions of substances in a sealed heated solution aboveambient temperature and pressure.

Solvothermal synthesis route was first proposed by Yi-Tai

Qian in 1996 (University of Science and Technology of

China), and is very similar to the hydrothermal route, the

only difference is the precursor solution is usually non-

aqueous but this is not always the case in all literature uses

of the expression.

Xie Y Qian YT*Wang WZ Zhang SYand Zhang YH A benzene-thermal synthetic route to nanocrystalline GaNSCIENCE, 272,1996, 1926

30nm


6/22

Apparatus in hydrothemal synthesis

autoclave

for cook

autoclave

formedicine

autoclave for

hydrothermal


7/22

Apparatus in hydrothemal synthesisThe autoclaves used in hydrothermal are usually thick-walledsteel cylinders with a hermetic seal which must withstand hightemperatures and pressures for prolonged periods of time.

Furthermore, the autoclave material must be inert with respectto the solvent. The closure is the most important element of theautoclave.

Many designs have been developed for seals, the most famous

being the Bridgman seal.In most cases steel-corroding solutions are used in hydrothermalexperiments. To prevent corrosion of the internal cavity of theautoclave, protective inserts are generally used. These may havethe same shape of the autoclave and fit in the internal cavity

(contact-type insert) or be a "floating" type insert which occupiesonly part of the autoclave interior. Inserts may be made ofcarbon-free iron, copper, silver, gold, platinum, titanium, glass (orquartz), or Teflon, depending on the temperature and solutionused.


8/22

Apparatus in hydrothemal synthesis

Commercially available autoclaves. (Courtesy of

M/S/ Toshin Kogyo Co. Ltd., Japan.)

Commercially available autoclaves. (Photo courtesy

of Parr Instruments Co., Illinois, USA.)


9/22

Schematic diagram of the

autoclave used in

hydrothermal / solvothermal

synthesis (1) stainless steel

autoclave (2) precursor

solution (3) Teflon liner (4)stainless steel lid (5) spring

autoclave used in my group


10/22

autoclave used inmy group


11/22

autoclave used in

my group


12/22

Characteristics ofCharacteristics of hydrothermal

synthesis

Generally, the hydrothermal synthesis involvesGenerally, the hydrothermal synthesis involves

with the following two major characteristics:with the following two major characteristics:

1) The system is always at a1) The system is always at a nonnon--idealideal andand nonnon--

equilibriumequilibrium state;state;2) The solvent is always at its2) The solvent is always at its nearnear--criticalcritical,,

criticalcritical oror supercritical statesupercritical state..


13/22


synthesis

Advantages of hydrothermal / solvothermal synthesis:

1) Most material can be made soluble in proper solvent by heating and

pressuring the system close to its critical point;2) Significant improvement in the chemical activity of the reactant, the

possibility to replace the solid-state synthesis, and materials whichmay not be obtained via solid-state reaction may be preparedthrough hydrothermal / solvothermal synthesis;

3) Products ofintermediate state, metasable state and specific phasemay be easily produced, novel compounds of metastable state andother specific condensed state may be synthesized;

4) Easy and precise control of the size, shape distribution, crystallinity

of the final product through adjusting the parameters such asreaction temperature, reaction time, solvent type, surfactant type,precursor type an the like.

5) Substances which are low in melting-points, high in vapor pressuresand tend to go pyrolysis will be obtained.


14/22


synthesis

Disadvantages of hydrothermal / solvothermal

synthesis:

1) The need of expensive autoclaves;1) The need of expensive autoclaves;

2) Safety issues during the reaction process;2) Safety issues during the reaction process;3) Impossibility of observing the reaction3) Impossibility of observing the reaction

process (process (black boxblack box))


15/22

Applications of hydrothermal synthesisApplications of hydrothermal synthesis

in the preparation ofin the preparation ofnanomaterialsnanomaterials

The hydrothermal method has been firstly proposedThe hydrothermal method has been firstly proposed

toto simulatesimulate the genetic condition of geologicalthe genetic condition of geologicalminerals;minerals;

Later, it has been adopted in the synthesis ofLater, it has been adopted in the synthesis ofmolecular sievesmolecular sieves and the crystal growth;and the crystal growth;

Now, with different starting materials, solvents,Now, with different starting materials, solvents,reaction temperatures as well as other experimentalreaction temperatures as well as other experimentalparameters, people have reported the synthesis ofparameters, people have reported the synthesis of

various kinds of nanostructures through hydrothermalvarious kinds of nanostructures through hydrothermal//solvothermalsolvothermal approaches includingapproaches including metal oxidesmetal oxides,,carbonaceouscarbonaceous nanostructures and etc.nanostructures and etc.


16/22

Applications of hydrothermal synthesisApplications of hydrothermal synthesis

in the preparation ofin the preparation ofnanomaterialsnanomaterials

Hydrothermal /Hydrothermal /solvothermalsolvothermal synthesis ofsynthesis of

zeoliteszeolites Hydrothermal /Hydrothermal /solvothermalsolvothermal synthesis ofsynthesis of

metal oxidesmetal oxides

Hydrothermal /Hydrothermal /solvothermalsolvothermal synthesis ofsynthesis ofcarbonaceous materialcarbonaceous material

Hydrothermal /Hydrothermal /

solvothermalsolvothermal

synthesis ofsynthesis of

nanowiresnanowires

OtherOther strategiesstrategies for hydrothermal /for hydrothermal /

solvothermalsolvothermal synthesissynthesis


17/22

Hydrothermal /Hydrothermal /solvothermalsolvothermal synthesissynthesis

ofofzeoliteszeolites


18/22

Hydrothermal /Hydrothermal /solvothermalsolvothermal

synthesis ofsynthesis ofzeoliteszeolites Zeolites are microporous crystalline materials that have been the most widely used

catalysts in industrial processes such as oil refining and petrochemistry. Theextension of their sole micropores into hierarchical pore systems consisting of bothmicropores and mesopores is nowadays demanded specifically for catalyzing largemolecules having dimensions in the mesoporous region (2-50 nm). Suchhierarchically porous zeolites or mesoporous materials with zeolitic characteristicsare known to solve the phenomena of slow diffusion and coke formation, resultingin pore blockage and catalyst deactivation, that are often encountered during theheterogeneous catalytic reactions of bulky molecules.

There are 46 known zeolite minerals in nature and over 175 synthetic zeolitesknown in the literature. The number of synthetic zeolites is increasing day by day,particularly after the discovery of aluminophosphate zeolites by Wilson et al.(1982). Despite the remarkable structural diversity in aluminophosphate zeolites,the product compositions are very similar:

xR + Al2O3 + (1.00.2) P2O5 + yH2O

whereR is an amine or quaternary ammonium ion.


19/22


synthesis ofsynthesis ofzeoliteszeolitesMicroporous Zeolite-Type Materials Basic structure of zeolite framework

Breck, D. W.,

ZeoliteMolecular

Sieves: Structure,

Chemistry and

Use, Wiley &

Sons, London

(1974)

Breck, D. W.,

Structure of

Zeolite, in:Zeolite

Molecular Sieves,

pp. 29185,

Wiley

Interscience

Publication, NewYork (1974)


20/22


synthesis ofsynthesis ofzeoliteszeolites The mechanisms of zeolite formation are very complex due to

the plethora of chemical reactions, equilibria, and solubility

variations that occur through the heterogeneous synthesismixture during the crystallization process.

Generally, the hydrothermal synthesis of zeolites involvesseveral steps, as shown below:

Reactant

Reactant mixtures

Nucleation

Crystal Growth


21/22


synthesis ofsynthesis ofzeoliteszeolites

For example, by using trialkoxysilylated alkyl

poly(oxyethylene ether) as mesopore-directingagent, a hierarchically porous siliceous MFI

zeolite (silicalite-1) with narrow mesoporosity

has been hydrothermally synthesized. A

mesostructured silica-surfactant composite was

formed at the early stage of the reaction, andzeolite crystallization proceeded during

subsequent hydrothermal treatment.

Rino R. Mukti et al,Langmuir2010, 26(4), 27312735


22/22


synthesis ofsynthesis ofzeoliteszeolites

SEM images of

mesoporous silicalite-1after hydrothermal

synthesis for (a) 2 days

and (b) 3 days. The

images for the (c)

product prepared with

C16EO10 and (d)

conventional silicalite-1

after hydrothermal

synthesis for 2 days arealso shown for

comparison.

Rino R. Mukti et al,Langmuir2010, 26(4), 27312735

100408 no.04-hydrothermal synthesis of nanomaterials-guo(1)

Documents